It is known to apply a Thermal Barrier Coating (TBC) to a surface of a component which operates at an elevated temperature. Thermal barrier coatings typically have low thermal conductivity, and therefore, in use, display a large temperature gradient across the thickness of the coating. Accordingly, thermal barrier coatings provide thermal insulation to components and thus allow the components to operate under large and prolonged heat loads. Furthermore, thermal barrier coatings may extend the life of the component by reducing oxidation and by reducing cyclic loading caused by temperature variations which may result in thermal fatigue.
Thermal barrier coatings are commonly applied to metallic components which are subjected to high-temperature conditions. For example, thermal barrier coatings are widely used within gas turbine engines, particularly on combustor rings, nozzle guide vanes, turbine blades, etc.
Thermal barrier coatings may be applied to a component using a number of techniques. For example, a thermal barrier coating may be applied using a physical vapour deposition technique (e.g. electron beam or laser beam deposition), direct vapour deposition, plasma spraying, electrostatic spray assisted vapour deposition, etc.
It is known to provide an interior surface of a circular combustor ring with a thermal barrier coating. To achieve this, the combustor ring is located within a TBC spray-chamber with the TBC spray nozzle located approximately at the centre of the circular combustor ring and in alignment with the interior surface. The TBC spray nozzle and combustor ring may be rotated relative to one another, such that the thermal barrier coating from the TBC spray nozzle covers the entire circumferential interior surface. This may be achieved by rotating the combustor ring using a rotary table or by rotating the TBC spray nozzle.
However, for the purposes of assembling the combustor a circumferential portion of the interior surface of the combustor ring is left uncoated. Accordingly, this portion of the interior surface is covered by a special adhesive TBC-proof tape, which masks the portion from the thermal barrier coating. The application and subsequent removal of the adhesive tape is carried out by hand and as a result is a slow and correspondingly expensive procedure. Furthermore, the current method is wasteful since the tape (approximately 5 m of tape per combustor ring) is discarded after every use.
The present invention seeks to overcome some or all of the problems associated with the prior art method described above.